Summary

Description

Aglaothamnion diaphanum is a pale pink coloured red seaweed, 2-10 mm high, with a delicate texture. The fronds are branched in one plane, with a single principal axis and linear to fan-shaped (flabellate) outline. This species shows little variation except in the degree of development of branching. In some thalli, occasional branching become equal in length to the main axis, producing a fan-shape (flabellate) rather than linear frond outline.

Recorded distribution in Britain and Ireland

This rare species is known in the British Isles from only a few records from the Isles of Scilly.

Global distribution

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Habitat

Usually grows on large algae as an epiphyte but also on bedrock, and rarely found growing on pebbles. This subtidal species grows from 7-25 m depth and can tolerate moderately wave exposed sites.

Depth range

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Identifying features

Uninucleate vegetative cells.

Zig-zag or U-shaped short side branches (carpogonial branches).

Thalli consisting of one to a few erect axes attached by small discoid filamentous holdfast and secondary creeping axes.

Hairs are abundant on female plants but absent during the spore-producing phase in the life cycle (bisporophytes).

Additional information

Could be confused with very small non-reproductive thalli of some growth forms of Compsothamnion gracillimum but Compsothamnion species are multinucleate in contrast to Aglaothamnion, which is uninucleate. Thalli reproductive from a small size and are usually easily recognisable by the reproductive spores (bisporangia). Identification of single specimens can be difficult, so if possible a number of thalli should be collected.

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